Pitch suppressing system

ABSTRACT

A system for suppressing forward pitching of the sprung mass portion of a vehicle during braking maneuvers, the system including a cylinder connected to the vehicle sprung mass, a rod connected to the unsprung mass and having a piston thereon slidable within the cylinder, a conduit between the chambers of the cylinder defined by the piston, a working fluid in the chambers and the conduit, an electrically actuated valve in the conduit for blocking the latter, and a switch responsive to operation of the vehicles&#39;&#39;s service brake for actuating the valve, the valve being operative when actuated by the switch to prevent fluid flow through the conduit between the chambers thereby to lock the cylinder and rod for suppressing relative movement between the sprung and the unsprung mass portions.

United States Patent 1191 Aldrich Nov. 27, 1973 PITCH SUPPRESSING SYSTEMPrim ary Examiner-Philip Goodman Assistant Examiner-John A. Carroll [75]Inventor. Fredric C. Aldrich, Lansing, Mich. Atmmey warren E. Finken etal- [73] Assignee: General Motors Corporation,

Detroit, Mich. 57] ABSTRACT [22] Filed: June 1972 A system forsuppressing forward pitching of the [21] Appl. No.: 261,032 sprung massportion of a vehicle during braking maneuvers, the system including acylinder connected to the vehicle sprung mass, a rod connected to theun- I (g1 280/124 Sprung mass and having a piston thereon slidable Iwithin the cylinder a conduit between the Chambers [58] Fleld of Search280/124 R, 1241 f h d d d b h fl 188/313 318 o t ecym er eme ytep1ston,awor mg u1 1n the chambers and the conduit, an electricallyactu- 56] References Cited ated valve in the conduit for blocking thelatter, and a switch responsive to operation of the vehicless serviceUNITED STATES PATENTS brake for actuating the valve, the valve beingopera- 3,537,715 11/1970 Gualdoni 280/124 R tive when actuated by theswitch to prevent fluid flow 3,176,801 4/1965 Huff 138/313 through theconduit between the chambers thereby to 3171057 1/1914 f---" 188/313lock the cylinder and rod for suppressing relative 2.553.912 S/l95lGervals 188/313 movement between the sprung and the unsprung massportions.

1 Claim, 1 Drawing Figure PITCH SUPPRESSING SYSTEM This inventionrelates generally to vehicle suspension arrangements and moreparticularly to a system for suppressing vehicle pitch during braking.

The primary feature of this invention is that it provides an improvedpitch suppressing system adapted particularly for incorporation in therear suspension system of an automobile type vehicle to suppress theforward pitch of the latter typically associated with vehicle brakingmaneuvers. Another feature of this invention is that it provides animproved vehicle pitch suppressing system including an electricallyactuatable locking unit disposed between the sprung and the unsprungmass portions of the vehicle and a switch for acmating the locking unitto a locked condition wherein relative jounce and rebound deflectionbetween the sprung and unsprung mass portions is prevented, the switchbeing controlled by the vehicle brake pedal so that the locking unit isactuated to the locked condition whenever the brake is applied. Yetanother feature of this invention resides in the provision of a lockingunit including a cylinder connected to the sprung mass portion of thevehicle, a rod extending through the cylinder and connected to theunsprung mass portion of the vehicle, a piston on the rod dividing thecylinder into a pair of variable volume chambers, and a conduit with anelectrically actuatable valve therein disposed between the variablevolume chambers, the chambers and the conduit being filled with anincompressible working fluid which is normally pumped by the pistonbetween the chambers but which locks the piston relative to the cylinderwhen the conduit is blocked by the valve member electrically actuated inresponse to application of the vehicles service brake. A still furtherfeature of this invention resides in the provision in the locking unitof a parallel path conduit providing communication between the variablevolume chambers, independently of the first mentioned conduit, theparallel path conduit having a check valve therein adapted, dependingupon the location of the locking unit, to permit one mode of deflectionwhile automatically preventing the other.

The foregoing and other featuresof this invention will be readilyapparent from the following specification and from the single drawingFIGURE showing the pitch suppressing system according to this inventionin an automobile suspension system enviroment.

Referring now to the single drawing FIGURE, thereshown is partiallybroken away side elevation is a portion of an automobile type vehicleincluding a longitudinally extended frame rail 10. The rail is one of apair of identical, transversely spaced, and rigidly interconnected railswhich form the frame of the vehicle. The rail 10 includes, toward therear end thereof, an arched portion 12 which extends above atransversely oriented rear axle assembly 14. The rear axle assemblyincludes a conventional differential carrier 16 situated generally inthe longitudinal plane of the symmetry of the vehicle between the framerails. The axle assembly further includes a pair of axle tubes rigidlyattached to the carrier and extending transversely from opposite sidesof the latter, only axle tube 18 being shown in the FIGURE. The axletubes rotatably support therewithin respective ones of a pair of axleshafts driven, through conventional gearing within the differentialcarrier 16, by a drive shaft 20 extending between the transmission ofthe vehicle, not shown, and the differential carrier, only axle shaft 21beingshown in the FIGURE. A pair of rear wheels are rotatably disposedat the outboard ends of the axle tubes and are conventionally driven bycorresponding ones of the axle shafts, only one rear wheel 22 beingshown in broken lines in the FIGURE.

As in conventional, the rear wheels and the rear axle assembly 14constitute a part of the unsprung mass portion of the vehicle while theframe, including the rail 10, constitutes a part of the sprung massportion of the vehicle, the sprung mass portion being supported abovethe unsprung mass portion by conventional spring means, not shown,disposed therebetween. Accordingly, forces on the unsprung mass portionresulting from road irregularities initiate relative jounce deflectionbetween the mass portions wherein the rear axle assembly 14 approachesthe rail 10 or relative rebound deflection between the mass portionswherein the rear axle assembly moves away from the rail 10. Further,when the service brake system of the vehicle is actuated to deceleratethe latter, forward pitching of the vehicle typically results becausethe center of gravity of the vehicle is situated a substantial distanceabove the road. Such forward pitching causes the front of the vehicle todip and the rear to lift thus initiating relative rebound reflectionbetween the rail 10 and the rear axle assembly. To control this forwardpitching during vehicle braking maneuvers, a pitch suppressing systemaccording to this invention and designated generally 24 is provided.

The pitch suppressing system 24 includes a locking unit 26 disposedbetween the rear axle assembly 14 and the rail 10, it being understoodthat an identical locking unit, not shown, is disposed between thesecond frame rail and the rear axle assembly on theopposite side of thevehicle. The locking unit 26 includes a cylinder 28 sealingly closed atits opposite ends by a pair of cap members 30 and 32. The cylinder isoriented generally vertically and extends through an appropriate openingin the frame rail 10 and is pivotably connected to the latter at 34through a pair of lugs rigidly attached to the rail, only one lug 36being shown. A rod 38 is slidingly and sealingly supported in alignedapertures in respective ones of the cap members 30 and 32 and extendsalong the longitudinal axis of the cylinder. The lower endof the rod 38is pivotably connected at 40 to a bracket 42 rigidly attached, as bywelding, to the axle tube- 18. Accordingly, each relative jounce andrebound deflection between the rail 10 and the rear axle assemblyeffects sliding movement of the rod relative to the cylinder 28, the rodbeing of sufficient length to remain in sealing engagement with each ofthe cap members 30 and 32 throughout the range of relative movementbetween the rail 10 and the rear axle assembly.

The locking unit 26 further includes a piston 44 rigidly attached to therod 38 within the cylinder 28. The piston slidingly and sealinglyengages the inside diameter of the cylinder thereby to divide the latterinto a pair of unconnected variable volume chambers 46 and 48. Thechambers are, however, interconnected independently of the piston 44through a c-shaped conduit 50 extending between the cap member 30 and32. The chambers are further interconnected independently of the piston44 by a parallel path conduit 52 extending between opposite leg portionsof the conduit 50.

The variable volume chambers 46 and 48, as well as the conduits 50 and52, are completely filled with an incompressible working fluid 54 suchas ordinary hydraulic brake fluid. Accordingly, as the rail and the rearaxle assembly 14 experience relative jounce and rebound deflections thepiston 44 pumps the working fluid 54 between the variable volumechambers through the conduits 50 and 52.

The conduit 52 has disposed therein a valve member 56 which iselectrically actuatable between an open condition permitting unimpededfluid flow in the conduit and a closed condition completely terminatingsuch flow. The conduit 50 has disposed therein a check valve 58 adaptedto permit fluid flow between the variable volume chambers duringrelative jounce deflection between the rail 10 and the rear axleassembly and to terminate such flow during relative rebound deflectionbetween the rail and the rear axle assembly.

An electrical circuit is provided for actuating the valve member 56 andincludes a source of electrical potential 60 which may be the storagebattery of the vehicle. The circuit further includes a conductor 62extending between an electrical terminal of the valve member 56 and oneterminal of a normally open switch 64, a conductor 66 extending betweenthe source 60 and the other terminal of the switch 64, and a pair ofground conductors 68 electrically grounding the source 60 and the valvemember 56. The switch 64 includes a contactor portion 70 movable betweenan operative position, not shown, electrically connecting the conductors62 and 66 and an inoperative position, as shown, remote from theconductors. The contactor 70 is connected by a link 71 to a foot pedal72 pivotally supported at 74 on a portion of the vehicle body. The footpedal is also connected by conventional means, not shown, to the servicebrake system of the vehicle so that pivotal movement of the pedal 72simultaneously effects actuation of the service brake system andconnection between the conductors 62 and 66.

Describing now the operation of the pitch suppressing system 24, duringnormal vehicle operation when braking maneuvers are not required thetransient relative jounce and rebound deflections between the rail 10and the rear axle assembly 14 effect flow of the working fluid back andforth between the chambers 46 and 48. Depending upon the size of theconduits, there may be or may not be, as desired, throttling of theworking fluid to effect energy absorption. When, however, a brakingmaneuver is required the operator depresses the pedal 72 to actuate theservice brake system. Simultaneously, the conductor 66 is electricallyconnected to the conductor 62 through the contactor 70 thus completing acircuit from the source 60 through the valve member 56 to ground. Thevalve member 56 is thereby actuated from the open condition to theclosed condition terminating communication between the chambers 46 and48 through the conduit 50. Accordingly, since the check valve 58prevents fluid flow through the conduit 50 in response to relativerebound deflection between the rail 10 and the rear axle assembly, therod 38 is effectively locked relative to the cylinder 28 by the workingfluid during rebound deflection because the fluid is prevented fromflowing between the variable volume chambers by the valve member 56.With relative rebound deflection thus foreclosed, forward pitching ofthe vehicle is effectively suppressed.

It will, of course, be apparent to those skilled in the art that thecheck valve 58 continues to permit relative jounce deflection betweenthe rail and the rear axle assembly during periods of braking thereby tomaintain a smooth ride if a bump should be encountered. Further, it willbe apparent that the locking unit 26 might be disposed between the frameand the front wheel unsprung mass portions of the vehicle with the checkvalve 58 reversed to permit only relative rebound deflection. Stillfurther, each wheel of the vehicle might have associated therewith alocking unit 26. In any of these three installations, however, theresult is identical in that a solid link is automatically disposedbetween the sprung and unsprung mass portions of the vehicle when theservice brake is applied, the solid link effectively suppressing thetendency of the vehicle to pitch during braking maneuvers.

Having thus described the invention, what is claimed 1. In a vehicleincluding an unsprung mass portion, a sprung mass portion supported onsaid unsprung mass portion for jounce and rebound deflection relative tothe latter, a service brake system, and a manually operable controlmember associated with said brake system for selectively actuating thelatter to arrest traversing motion of said vehicle, the improvementcomprising, a cylinder member connected to one of said sprung and saidunsprung mass portions, a rod slidably disposed on said cylinder memberand extending axially of said cylinder member and completelytherethrough, means connecting said rod to the other of said sprung andsaid unsprung mass portion so that jounce and rebound deflectionstherebetween effects sliding movement of said rod relative to saidcylinder member, a piston rigidly attached to said rod and slidablydisposed within said cylinder member, said piston dividing said cylindermember into a pair of unconnected variable volume chambers adapted foralternate expansion and contraction in response to relative movementbetween said piston and said cylinder member, a first conduit remotefrom said piston for effecting communication between said variablevolume chambers, a second conduit remote from said piston for effectingcommunication between said variable volume chambers, an incompressibleworking fluid disposed in said variable volume chambers and in each ofsaid first and said second conduits, said working fluid being pumpedbetween said chambers in parallel paths through said first and secondconduits in response to movement of said piston relative to saidcylinder member, electrically operable valve means disposed in saidfirst conduit and actuable between an open condition and a closedcondition terminating communication between said variable volumechambers through said first conduit, a source of electrical potential,circuit means between said source and said valve means including aswitch responsive to operation of said control member for effectingactuation of said valve means to the closed condition thereof when saidbrake system is actuated, and a check valve disposed in said secondconduit for permitting flow of said working fluid between said variablevolume chambers independently of said first conduit during deflectionbetween said sprung and said unsprung mass portion in one of the jounceand rebound modes and for preventing such flow through said secondconduit during deflection between said sprung and said unsprung massportion in the other of the jounce and rebound modes.

1. In a vehicle including an unsprung mass portion, a sprung massportion supported on said unsprung mass portion for jounce and rebounddeflection relative to the latter, a service brake system, and amanually operable control member associated with said brake system forselectively actuating the latter to arrest traversing motion of saidvehicle, the improvement comprising, a cylinder member connected to oneof said sprung and said unsprung mass portions, a rod slidably disposedon said cylinder member and extending axially of said cylinder memberand completely therethrough, means connecting said rod to the other ofsaid sprung and said unsprung mass portion so that jounce and rebounddeflections therebetween effects sliding movement of said rod relativeto said cylinder member, a piston rigidly attached to said rod andslidably disposed within said cylinder member, said piston dividing saidcylinder member into a pair of unconnected variable volume chambersadapted for alternate expansion and contraction in response to relativemovement between said piston and said cylinder member, a first conduitremote from said piston for effecting communication between saidvariable volume chambers, a second conduit remote from said piston foreffecting communication between said variable volume chambers, anincompressible working fluid disposed in said variable volume chambersand in each of said first and said second conduits, said working fluidbeing pumped between said chambers in parallel paths through said firstand second conduits in response to movement of said piston relative tosaid cylinder member, electrically operable valve means disposed in saidfirst conduit and actuable between an open condition and a closedcondition terminating communication between said variable volumechambers through said first conduit, a source of electrical potential,circuit means between said source and said valve means including aswitch responsive to operation of said control member for effectingactuation of said valve means to the closed condition thereof when saidbrake system is actuated, and a check valve disposed in said secondconduit for permitting flow of said working fluid between said variablevolume chambers independently of said first conduit during deflectionbetween said sprung and said unsprung mass portion in one of the jounceand rebound modes and for preventing such flow through said secondconduit during deflection between said sprung and said unsprung massportion in the other of the jounce and rebound modes.